1. Field of the Invention
The invention relates to a bearing element with a metallic support body, a bearing metal layer arranged on top and a polymer layer arranged over the latter, whereby the polymer layer comprises a polyimide resin, molybdenum sulphide (MoS2) and graphite, a motor with a shaft which is mounted by a bearing element, whereby the bearing element comprises at least one metal support body and a bearing metal layer arranged over the latter, as well as the use of a lubricating varnish made from a polymer.
2. Prior Art
Coatings of tribologically stressed components or surfaces need to satisfy various different requirements. On the one hand, a coating is required that as low friction as possible, that is relatively soft and which can therefore adapt well to wear-related abrasion and lubricating partners. On the other hand, it needs to have a sufficiently high degree of mechanical stability and strength in order to absorb the static and the dynamic vibrational loads and thus increase its fatigue strength and lifetime. Developments, for example in the motor industry, are moving towards greater specific performance, in order to increase effectiveness in particular with respect to ever stricter standards relating to exhaust gas, and thereby increase the profitability and ecofriendliness of internal combustion engines. A large number of components in an internal combustion engine are affected by this development, such as for example the radial lubricating bearings that are highly stressed by very high torques and the continually increasing ignition pressures for optimising the combustion process, for example in a direct injection turbo diesel engine. By means of the high-performance injection systems of these engines the components of the injection pumps and their measuring instruments are also subject to these high stresses, or other components such as rams, pins or rollers are affected by the high loads. Aluminium alloys are frequently used for these components, as thereby a good ratio can be achieved between the properties obtained and the required costs.
The most recent developments in this field increasingly show the use of so-called lubricating varnishes—even though their use has been known about in principle for several years.
Thus, e.g. DE 22 06 400 A describes a bonding material with a metallic support body and a frictional or lubricating layer bonded by adhesive to the support body made of thermally highly resistant plastics, which contains thermosetting polyimide resins and additives improving the running properties of the bearing, such as polytetrafluoroethylene, metallic bearing alloys or the like, whereby the friction and/or the lubricating layer contains the polyimide resins and the additives improving the running property as a mixture of fine-grained or fine-powdered material, and contains polyimide varnish as the binding agent, which bonds the fine-grained or fine-powdered mixture in the frictional and/or lubricating layer as well as the frictional or lubricating layer itself to the support body. The lubricating layer can in this case contain between 70 and 20 wt. % thermosetting polyimide resins and about 30 to 80 wt. % self-lubricating additives. Graphite, molybdenum and oxides are named as the self-lubricating additives.
From EP 0 939 106 A a lubricating coating material is known which as a matrix material contains PTFE or PTFE in combination with other fluorothermoplasts, the melting point of which lies above 260° C., whereby at least one powdered polyaramide is included, the proportion of which relative to the total amount of PTFE or the mixture of PTFE and other fluorothermoplasts and the polyaramide is 10 to 50 vol. %.
Also in EP 1 236 914 A a lubricating bearing is described which has a resin coating on a bearing metal layer, whereby the resin coating has a thermosetting resin with specific physical properties in an amount from 70 to 30 vol. % with self-lubricating additives in an amount from 30 to 70 vol. %, and whereby the Vickers hardness level is not greater than 20. The resin can for example be a polyamide imide resin. Molybdenum disulphide, graphite, boron nitride, tungsten disulphide, polytetrafluoroethylene, lead etc. are named as self-lubricating additives.
Polymers for use as coating materials of lubricating elements are described in the following documents: U.S. Pat. No. 5,525,246 A, JP 60-1424 A, EP 0 984 182 A, JP 04-83914 A, JP 07-247493 A, GB 2 337 306 A, JP 09-79262 A, JP 2001/173644 A, DE 20 00 632 A, DE 33 43 309 A, DE 32 21 785 A, WO 97/38046 A, EP 0 340 839 A, EP 0 044 577 A, EP 0 340 838 A, DE 24 15 327 A, EP 060 725 A, DE 198 14 756 A, U.S. Pat. No. 4,618,270 A, DE 25 04 833 A, FR 21 33 320 A, GB 2 384 033 B, JP-53-007780 A.